perf(页面加载): 优化价格显示性能并添加加载状态处理

- 改用DOMContentLoaded事件提前初始化页面
- 实现渐进式价格显示：基础价格→加载中→实时价格
- 为fetchVisitData添加超时和重试机制
- 新增价格状态视觉区分样式
- 从2分钟等待优化为立即显示基础价格，后台异步更新

styles.css

@@ -48,6 +48,46 @@ main {
     display: grid;
     grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
     gap: 2rem;
+}
+
+/* 价格状态样式 */
+.base-price {
+    color: #666 !important;
+    font-style: italic;
+    position: relative;
+}
+
+.base-price::after {
+    content: " (基础价格)";
+    font-size: 0.8em;
+    color: #999;
+    font-weight: normal;
+}
+
+.loading-price {
+    color: #007bff !important;
+    animation: pulse 1.5s ease-in-out infinite;
+    font-weight: 500;
+}
+
+@keyframes pulse {
+    0% { opacity: 1; }
+    50% { opacity: 0.6; }
+    100% { opacity: 1; }
+}
+
+.real-time-price {
+    color: #28a745 !important;
+    font-weight: bold;
+    position: relative;
+}
+
+.real-time-price::after {
+    content: " (实时价格)";
+    font-size: 0.8em;
+    color: #28a745;
+    font-weight: normal;
+    opacity: 0.8;
     margin-bottom: 3rem;
 }
 
@@ -465,4 +505,4 @@ footer {
     font-size: 0.9em;
     font-weight: normal;
     margin-top: 4px;
-} 
+}